When infants and small children ride in a motor vehicle, it is recommended for safety reasons that they be restrained in an auxiliary child seat. Many types of auxiliary child seats are commercially available for infants/children of varying sizes and weights. Many of these auxiliary child seats are secured in place on a vehicle seat by the occupant restraint seatbelt that is primarily intended for restraining a full size occupant in the seat.
Surveys have shown that many vehicle operators do not properly install their auxiliary child seat in their vehicles, and consequently the effectiveness of the seat in protecting the infant or child may be reduced.
It would be desirable to provide a system by which a vehicle operator could be alerted to the fact that an auxiliary child seat installed in his/her vehicle is not properly installed, so that the operator can correct the potentially dangerous condition before driving the vehicle.
In the pursuit of greater safety for occupants of vehicles during a crash, many automotive vehicles are now or will soon be equipped with a seat occupant classification system for one or more of the passenger seats. An occupant classification system senses the size, weight, and/or position of a person or object present in the seat and provides this information to a restraints control module that uses the information to determine whether and to what degree to activate restraint systems during a crash or other high acceleration/deceleration event. Occupant classification systems use various types of sensors, including fluid-filled, pressure-sensing bladders and load-responsive electrical switches installed within the seat.
It is common for vehicles to be equipped with seatbelt buckle condition sensors that determine whether the buckle or latch of a seatbelt is in a fastened or unfastened condition. This information has been used for various purposes, including alerting the vehicle operator if one or more seat occupants have not fastened their seatbelts. U.S. Pat. No. 6,250,672 teaches an airbag restraint system in which the airbag is deactivated if an occupant classification sensor determine that a small-statured person or a child carrier seat is present in the passenger seat of a vehicle. A seatbelt buckle condition sensor is used to activate an airbag condition indicator light is illuminated if the seatbelt buckle is fastened, which will be the case only if a child carrier seat is present, thereby giving the vehicle operator a positive indication that the airbag is deactivated.
It is also known to provide a seatbelt tension sensor to detect the amount of tension present in a seatbelt when it is fastened around a seat occupant. The amount of tension in the belt may be used to derive a more accurate reading of seat occupant weight, since a taut belt may exert a downward force on the occupant that is detected by a seat weight sensor. The downward force contributed by the belt tension is subtracted from the total weight reading to get an actual seat occupant weight. A system that operates in this manner is disclosed in U.S. Patent Application Publication 2002/0043789A1.
A seatbelt tension monitoring system and associated occupant classification system is disclosed in U.S. patent application Ser. No. 10/177,442 titled “Method of Controlling Airbag Deployment,” filed by the applicant of the present application on 21 Jun. 2002, the disclosure of which is incorporated herein by reference.